chore: ignore local dev sqlite + generated schema artifacts

Local dev runs with the SQLite backend leave `wfe.db{,-shm,-wal}` files
in the repo root, and `workflows.schema.yaml` is a generated artifact
we prefer to fetch from the running server's `/schema/workflow.yaml`
endpoint rather than checking in.

.gitignore

@@ -4,3 +4,9 @@ Cargo.lock
 *.swo
 .DS_Store
 .env*
+# Local dev SQLite database + WAL companions
+/wfe.db
+/wfe.db-shm
+/wfe.db-wal
+# Auto-generated schema artifact (server endpoint is the source of truth)
+/workflows.schema.yaml